AudioService: permission for volume adjustment to lowest values

  Define an attenuation threshold under which the
MODIFY_AUDIO_SETTINGS permission is required to adjust volume.
  Verify permission at the interface of audio service, and
propagate this information so its used when getting a valid
index during a volume adjustment or set.
  Make the audio service dump display the min index when it
differs from the normal min index.
  Enforcement is only for STREAM_ALARM.

Bug: 137015603
Test: use POC app in bug, verify ALARM volume not at 1 with \
      adb shell dumpsys audio

Change-Id: I083a26fd8eeebd4e5434ed02a4a803cbb920ab84